Method for transitioning between multiple reception levels

ABSTRACT

There is provided a method for enabling a user equipment (UE) to transition between a non-discontinuous reception (Non-DRX) level and at least one discontinuous reception (DRX) level. The UE in a DRX level wakes up periodically to monitor a scheduling channel. The method includes receiving a DRX indicator in a Non-DRX level with continuously monitoring the scheduling channel and transitioning from the Non-DRX level to a DRX level indicated by the DRX indicator. The UE can transition between multiple DRX levels by an explicit command/signaling.

This application is a continuation of U.S. patent application Ser. No.12/311,803, filed Apr. 14, 2009, which is a national phase entry ofInternational Application No. PCT/KR2007/005368, filed on Oct. 30, 2007,and claims the benefit of U.S. Provisional Application No. 60/863,545,filed on Oct. 30, 2006, U.S. Provisional Application No. 60/884,401,filed on Jan. 10, 2007, and Korean Patent Application No.10-2007-0023636, filed on Mar. 9, 2007, the contents of each of theabove-recited applications are hereby incorporated by reference herein,for all purposes, in their entireties.

TECHNICAL FIELD

The present invention relates to wireless communication, and morespecifically, to a method for transitioning between multiple receptionlevels to minimize power consumption of a user equipment and to enhancequality of service in a wireless communication system.

BACKGROUND ART

Third generation partnership project (3GPP) mobile communication systemsbased on a wideband code division multiple access (WCDMA) radio accesstechnique are widely deployed all over the world. High speed downlinkpacket access (HSDPA) that can be defined as a first evolutionary stageof WCDMA provides 3GPP with highly competitive radio access technique inthe mid-term future. However, since requirements and expectations ofusers and service providers are continuously increased and developmentsof competing radio access techniques are continuously in progress, newtechnical evolutions in 3GPP are required to secure competitiveness inthe future. Decrease of cost per bit, increase in service availability,flexible use of frequency bands, simple architecture and open interface,low power consumption of a user equipment and the like are suggested asrequirements of next generation communication systems.

Paging is an activity of a network calling one or more user equipmentsfor a certain purpose. In addition to a basic function of enabling thenetwork to search for a user equipment, paging also has a function ofenabling the user equipment to be waken tip from a sleep mode. The userequipment is in the sleep mode in normal times. The user equipment wakesup only when a paging channel is arrived from the network and performsan action requested by the network.

In the sleep mode, the user equipment should periodically wake up andconfirm whether the paging channel is arrived. Waking up of the userequipment at periodic intervals, not at all times, is calleddiscontinuous reception (hereinafter, referred to as DRX).

Unlike a base station, the user equipment operates using a battery. Ifthe battery of the user equipment is not continuously recharged, therunning time of the user equipment is limited. To increase the runningtime, the user equipment should be designed so as to minimize powerconsumption when the user equipment does not actually transmit orreceive data.

There are various methods to save power consumption. A first method thatconforms to the design criteria established due to the limited capacityof the battery of the user equipment is to minimize the time spent forthe user equipment to confirm whether any data has been arrived at theuser equipment. The time spent for the user equipment to monitor achannel that notifies arrival of data to the user equipment, such as apaging channel, is minimized. A second method is to transfer user datato the user equipment with a minimum delay time when there is the userdata to be transferred from the network to the user equipment. Thelonger the time is taken from the point when the user data is created bythe network to the point when the user data actually arrives at the userequipment, the more the quality of service felt by the user is degraded.The user data arrived at the network should be transferred to the userequipment as soon as possible in order to minimize the delay time.However, in order to reduce the delay time, the time spent for the userequipment to observe a paging channel t, such as a paging channel,should be increased.

Although the first and second methods described above are indispensableconditions for optimally operating the user equipment, they areconditions contradict to each other.

There is a need for a method for simultaneously satisfying both of thetwo conditions in the user equipment and the network.

DISCLOSURE OF INVENTION Technical Problem

It is an object of the invention to provide a method for enabling a userequipment to transition between multiple reception levels throughexplicit signaling, thereby minimizing power consumption of the userequipment and preventing degradation in quality of service.

Technical Solution

In one aspect, there is provided a method for enabling a user equipment(UE) to transition between a non-discontinuous reception (Non-DRX) leveland at least one discontinuous reception (DRX) level. The UE in a DRXlevel wakes up periodically to monitor a scheduling channel. The methodincludes receiving a DRX indicator in a Non-DRX level with continuouslymonitoring the scheduling channel and transitioning from the Non-DRXlevel to a DRX level indicated by the DRX indicator.

In another aspect, there is provided a method for enabling a userequipment (UE) to transition between a plurality of reception levels.The method includes receiving transition information in a firstreception level and transitioning from the first reception level to asecond reception level based on the transition information.

In still another aspect, there is provided a method for enabling a userequipment (UE) to transition between a plurality of reception levels.The method includes detecting a transition condition and transitioningfrom a first reception level to a second reception level when thetransition condition is detected. The DRX level period of the firstreception level is different from that of the second reception level.

Advantageous Effects

A user equipment can transition between multiple DRX levels by anexplicit command/signaling. Power consumption of the user equipmentincurred by waiting when the user equipment transmits and/or receivesdata is minimized, and quality of service can be optimized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a radio communication system.

FIG. 2 is a block diagram showing a control plane of a radio interfaceprotocol.

FIG. 3 is a block diagram showing a user plane of a radio interfaceprotocol.

FIG. 4 is an example showing a method of receiving data according to anembodiment of the present invention.

FIG. 5 is an example showing a method of receiving data according toanother embodiment of the present invention.

FIG. 6 is an example showing a method of receiving data according tostill another embodiment of the present invention.

FIG. 7 is an example showing a method of receiving data according tostill another embodiment of the present invention.

FIG. 8 is an example showing a method of receiving data according tostill another embodiment of the present invention.

FIG. 9 is an example showing a method of receiving data according tostill another embodiment of the present invention.

FIG. 10 is an example showing a method of receiving data according tostill another embodiment of the present invention.

FIG. 11 is an example showing a method of receiving data according tostill another embodiment of the present invention.

FIG. 12 is an example showing a method of transmitting data according toan embodiment of the present invention.

MODE FOR THE INVENTION

FIG. 1 is a block diagram showing a wireless communication system. Itcan be a network structure of an evolved-universal mobiletelecommunication system (E-UMTS). The E-UMTS can be referred to as along term evolution (LTE) system. The wireless communication system iswidely deployed to provide a variety of communication services, such asvoices, packet data, and the like.

Referring to FIG. 1, an evolved-UMTS terrestrial radio access network(E-UTRAN) includes a base station (BS) 20. A user equipment (UE) 10 canbe fixed or mobile and can be referred to as another terminology, suchas a mobile station (MS), a user terminal (UT), a subscriber station(SS), a wireless device or the like. The BS 20 generally is a fixedstation that communicates with the UE 10 and can be referred to asanother terminology, such as an evolved-NodeB (eNB), a base transceiversystem (BTS), an access point or the like. One or more cells can existwithin the scope of the BS 20. An interface for transmitting usertraffics or control traffics can be used between BSs 20. Hereinafter, adownlink means a communication from the BS 20 to the UE 10, and anuplink means a communication from the UE 10 and the BS 20.

The BS 20 provides termination points of the user plane and the controlplane. The BSs 20 are connected to each other through an X2 interface,and adjacent base stations 20 can have a network of a meshed structurewhere the X2 interface always exists.

The BS 20 is connected an evolved packet core (EPC), furtherspecifically, to an access gateway (aGW) 30, through an S1 interface.The aGW 30 provides a termination point of a session and mobilitymanagement function of the user equipment 10. Between the BS 20 and theaGW 30, a plurality of nodes can be connected to each other in amany-to-many relation through the S1 interface. The aGW 30 can bedivided into a part for processing user traffics and a part forprocessing control traffics. In this case, an aGW for processingtraffics of a new user can communicate with an aGW for processingcontrol traffics through a new interface. The aGW 30 is also referred toas a mobility management entity/user plane entity (MME/UPE).

Layers of the radio interface protocol between the UE and the BS can bedivided into L1 (a first layer), L2 (a second layer) and L3 (a thirdlayer) based on the lower three layers of the open systeminterconnection (OSI) model that is well-known to communication systems.A physical layer corresponding to the first layer provides aninformation transfer service using a physical channel. A radio resourcecontrol (RCC) layer placed in the third layer controls radio resourcesbetween the UE and the network. For this purpose, the RRC layerexchanges RRC messages between the UE and the network. The RRC layer canbe distributed among network nodes, such as the BS 20, the aGW 30 andthe like, or can be located only in the BS 20 or the aGW 30.

The radio interface protocol includes the physical layer, a data linklayer and a network layer in the horizontal plane. Or the radiointerface protocol includes a user plane for transmitting datainformation and a control plane for transferring control signals in thevertical plane.

FIG. 2 is a block diagram showing the control plane of the radiointerface protocol. FIG. 3 is a block diagram showing the user plane ofthe radio interface protocol. These show the structure of the radiointerface protocol between a UE and a E-UTRAN based on the 3GPP radioaccess network specification.

Referring to FIGS. 2 and 3, a physical layer, i.e., a first layer,provides an information transfer service to upper layers using aphysical channel. The physical layer is connected to a medium accesscontrol (MAC) layer, i.e., an upper layer, through a transport channel.Data are moved between the MAC layer and the physical layer through thetransport channel. Between different physical layers, i.e., the physicallayer of a transmitter and the physical layer of a receiver, data aremoved through the physical channel.

The MAC layer of a second layer provides a service to a radio linkcontrol (RLC) layer, i.e., an upper layer, through a logical channel.The RLC layer of the second layer supports reliable data transfer. Thefunction of the RLC layer can be implemented as a functional blockwithin the MAC layer and in this case, the RLC layer may not exist asshown in dotted line.

A packet data convergence protocol (PDCP) of the second layer performsheader compression function to reduce the size of an IP (InternetProtocol) packet header containing relatively large and unnecessarycontrol information in order to efficiently transmit packets in a radiosection of a narrow bandwidth when transmitting IP packets such as IPv4or IPv6 packets.

A radio resource control (RRC) layer of a third layer is defined only onthe control plane. The RRC layer controls the logical channel, thetransport channel and the physical channel in relation withconfiguration, reconfiguration and release of a radio bearer (RB). TheRB means a service provided by the second layer to transfer data betweenthe UE and the E-UTRAN. The RB means a logical path provided by thefirst and second layers of the radio protocol to transfer data betweenthe UE and the E-UTRAN. Generally, setting an RB means a process ofspecifying characteristics of the radio protocol layers and channelsneeded for providing a specific service and setting specific parametersand operating methods of the radio protocol layers and channels.

A downlink transport channel for transmitting data from the network tothe UE includes a broadcast channel (BCH) for transmitting systeminformation and a downlink-shared channel (DL-SCH) for transmitting usertraffics or control messages. Traffics for multicast or broadcastservice or control messages can be transmitted through the DL-SCH or aseparate downlink-multicast channel (DL-MCH). An uplink transportchannel for transmitting data from the UE to the network includes arandom access channel (RACH) for transmitting initial control messagesand an uplink-shared channel (UL-SCH) for transmitting other usertraffics or control messages. A paging channel (PCH) for transferringpaging information is also included in the uplink transport channel.

FIG. 4 is an example showing a method of receiving data according to anembodiment of the present invention.

Referring to FIG. 4, a UE has at least two discontinuous reception(hereinafter, referred to as DRX) levels. The DRX level defines a momentfor the UE to confirm arrival of downlink data. The DRX level is areception level for reducing power consumption of the UE. The DRX leveldefines a period for confirming arrival of downlink data, i.e., a DRXlevel period. The UE confirms arrival of downlink data at every DRXlevel period. A time point in the DRX level period at which the UEconfirms arrival of downlink data is called as a paging occasion. Thepaging occasion can be repeated in every DRX level period.

An interval at which radio resources are allocated to the UE is calledas a transmission time interval (TTI), and the paging occasion can pointa first TTI in the DRX level period.

The DRX level period of each DRX level can be different from those ofother DRX levels. There is a plurality of DRX levels having DRX levelperiods different from each other.

Hereinafter, it is assumed that the UE has two DRX levels, i.e., a firstDRX level and a second DRX level, and the DRX level period of the firstDRX level is longer than the DRX level period of the second DRX level.However, the number of DRX levels is not limited to two, but can bethree or more.

The UE wakes up at the first subframe of the first DRX level andreceives a scheduling channel. Here, the scheduling channel means achannel that indicates arrival of data to the UE or transmits a pagingsignal to the UE. The scheduling channel may be a paging indicatorchannel (PICH), a paging channel (PCH), an L1/L2 control channel and thelike.

In FIG. 4, since the UE cannot find its information from the firstsubframe of the first DRX level, it enters into a sleep mode during theremaining DRX level period.

Next, the UE wakes up at the first subframe of the first DRX levelperiod and receives the scheduling channel. If the BS has a first dataD1 to transmit, the BS informs the UE of the existence of the first datain line with the starting point of the first DRX level period throughthe scheduling channel. The UE recognizes that it has been scheduled andoperates in a non-discontinuous reception (Non-DRX) level. The Non-DRXlevel may also be called as a continuous reception level. In the Non-DRXlevel, the UE continuously receives a channel directing to receive dataor a channel informing arrival of data to be transferred to the UE. Ifthe BS has the first data D1 to transmit, the BS informs the UE of theexistence of the first data through the scheduling channel. The UErecognizes the scheduling channel, enters into the Non-DRX level, andreceives the first data D1 as indicated by scheduling information.

After completing transmission of the first data D1, the BS transmits aDRX indicator to the UE to inform that the UE does not need tocontinuously receive the scheduling channel any more.

The DRX indicator directs the UE to transition to a new reception level.The DRX indicator becomes a transition condition for transitioning theUE to the new reception level. The new reception level can be a new DRXlevel or a new Non-DRX level. The BS can direct the UE to transitionfrom the Non-DRX level to the first or second DRX level through the DRXindicator. In the example of FIG. 4, the DRX indicator directs the UE totransition to the second DRX level and the UE transitions from theNon-DRX level to the second DRX level as indicated by the DRX indicator.If the second DRX level is not set, the UE can transition to the firstDRX level.

While operating in the second DRX level, the UE wakes up at the firstsubframe of each second DRX level period and receives the schedulingchannel. If the BS has a second data D2 to transmit, the BS informs theUE of the existence of the second data D2 in line with the second DRXlevel period through the scheduling channel. The UE recognizes thescheduling channel, enters into the Non-DRX level and receives thesecond data D2. Since the second DRX level period is shorter than thefirst DRX level period, the BS can transmit the second data D2 atfurther short intervals.

If the UE cannot find its information from the scheduling channel duringthe remaining period of the second DRX level period, the UE does notreceive the scheduling channel in the remaining period. The UE wakes upat the first subframe of each second DRX level period and receives thescheduling channel. If it cannot find its information from the firstsubframe of the second DRX level period, the UE does not receive thescheduling channel during the remaining period of the second DRX levelperiod of the corresponding second DRX level.

If a certain condition is satisfied while operating in the second DRXlevel, the UE can transition to the first DRX level again. Here, it isshown in the figure that as soon as the second period of the first DRXlevel period is over at the BS, i.e., the third period of the first DRXlevel period starts, the UE stops operating in the second DRX level andtransitions to the first DRX level.

At least two or more reception levels are defined between the networkand the UE.

The reception level means a reception state of the UE, which can be aNon-DRX level or a DRX level. When a transition condition is satisfied,the UE can transition between the reception levels.

The reception levels are transitioned by an explicit command or anexplicit signaling.

One example of the transition condition for transitioning between thereception levels is that the UE receives a DRX indicator. The DRXindicator can direct the UE to transition to another DRX level. Also theDRX indicator can direct the UE to transition to the Non-DRX level. TheDRX indicator can contain information indicating to which receptionlevel the UE should transition among a plurality of reception levels. Ifthe UE receives the DRX indicator on whether the UE should transition toa specific DRX level, the UE transitions to the DRX level directed bythe DRX indicator.

The DRX indicator can contain information indicating when the UEtransitions to a new DRX level. The DRX indicator can contain a starttime of the new DRX level. If the DRX indicator contains informationindicating when the UE should transition to the new DRX level, the UEcan transition to the new DRX level at the time directed by theinformation.

The DRX indicator can be transmitted through the L1/L2 control channel.Alternatively, the DRX indicator can be transmitted through a MACmessage and the DRX indicator can be contained in the MAC header. TheDRX indicator contained in the MAC header can be contained in the MACprotocol data unit (PDU) in the form of control information. The DRXindicator can be transmitted through an RRC message.

Another example of the transition condition is that the UE receives asetting value of a new reception level. The BS can inform the UE of thesetting value when the network and the UE initially establish a call orreestablish the call. The setting value can be a value related to a DRXlevel period used in each DRX level. Alternatively, the setting valuecan be information indicating when a DRX level period begins in each DRXlevel. The setting value can be transferred through an RRC message.

Still another example of the transition condition is that the UE doesnot receive data for a specific period of time, or the UE is notnotified for a specific period of time with arrival of data that the UEshould receive through a channel directing the UE to receive data or achannel informing existence of data to be transferred to the UE.

Still another example of the transition condition is that the UEtransmits data through an uplink channel. This is a case where the UEtransmits a message for requesting radio resources to the uplink channelor transmits user data or a control message through the uplink channel.

Still another example of the transition condition is starting of a newDRX level period of a DRX level that is different from the DRX level inwhich the UE is currently stays.

Still another example of the transition condition is starting of a newDRX level period of another DRX level having a DRX level period that islonger than the DRX level period of the DRX level in which the UE iscurrently stays.

If a transition condition is occurred and the UE transitions to a newDRX level, the new DRX level can be applied from a specific time. Thespecific time can be a time point at which a new period of the new DRXlevel starts. When the UE transitions to the new DRX level, the UE canmaintain the currently used DRX level until the new period of the newDRX level is started.

In each DRX level, the UE receives a scheduling channel which directsthe UE to receive data or informs existence of data to be transferred tothe UE at predetermined time periods. After receiving the schedulingchannel, if the UE is notified with existence of data arrived at the UEor receives information on radio resources that the UE should receive,the UE can transition to a new reception level. For example, the UE cantransition to the Non-DRX level. If the BS notifies the UE that there isno data arrived at the UE or the UE is not notified with information onradio resources that the UE should receive, the UE does not receive thescheduling channel until the next predetermined time period based on theDRX setting value.

In each DRX level, the BS can transmit a DRX indicator directing toreceive data or commanding to prepare to receive data only atpredetermined time periods through the scheduling channel. Afterreceiving the DRX indicator, the UE can transition to a new receptionlevel. For example, the network and the UE can transition to the Non-DRXlevel. If the BS notifies the UE that there is no data arrived at the UEor does not notify the UE of information on radio resources that the UEshould receive, the BS may not transmit the DRX indicator until the nextpredetermined time period based on the DRX setting value.

The predetermined time period can be a paging occasion. The pagingoccasion repeats in every DRX level period. The paging occasion is thefirst TTI of the DRX level period.

Hereinafter, a plurality of reception levels and transitionstherebetween is described with examples.

A network and a UE can set three reception levels. The three receptionlevels include a Non-DRX level and two DRX levels (a first DRX level anda second DRX level). The network and the UE transition from the currentreception level to the next reception level if a certain condition issatisfied. Then, they set a method of receiving a downlink channel basedon the setting value set to each of the reception levels.

In the Non-DRX level, the UE continuously receives a scheduling channeldirecting the UE to receive data or informing existence of data to betransferred to the UE. In the Non-DRX level, the UE continuouslyreceives the scheduling channel at every time period.

In the first DRX level, the UE receives the scheduling channel at everypaging occasion based on the DRX setting value (DRX level period). Ifexistence of data to be transferred to the UE is indicated orinformation on allocation of radio resources that the UE should receiveis received in the paging occasion, the UE can transition to the Non-DRXlevel.

In the second DRX level, the UE receives a scheduling channel directingthe UE to receive data at every paging occasion based on the DRX settingvalue. If existence of data to be transferred to the UE is indicated orinformation on allocation of radio resources that the UE should receiveis received in the paging occasion, the UE can transition to the Non-DRXlevel. Alternatively, the UE can transition from the second DRX level tothe first DRX level.

In the second DRX level, the UE receives a scheduling channel directingthe UE to receive data at every paging occasion based on the DRX settingvalue. If existence of data to be transferred to the UE is indicated orinformation on allocation of radio resources that the UE should receiveis received in the paging occasion, the UE can perform continuousreception only for a corresponding period of the second DRX level.During the whole corresponding period, the UE can receive the schedulingchannel.

One example of the transition condition for the UE to transition fromthe Non-DRX level to the second DRX level is that the UE receives a DRXindicator directing to transition to the second DRX level from the BS.Another example is that the UE does not receive data from the BS for acertain period of time or does not receive scheduling information. Stillanother example is that the UE receives a setting value for a newNon-DRX level. Still another example is that while the UE does notreceive data for a certain period of time or information on datascheduling of the UE from the BS, the UE arrives at the first subframeof the second DRX level period.

One example of the transition condition for the UE to transition fromthe second DRX level to the first DRX level is that the UE does notreceive data from the BS for a certain period of time or does notreceive scheduling information. Another example is that the UE does notreceive data from the BS or does not receive information on datascheduling for the UE. Still another example is that the UE arrives atthe first subframe of the first DRX level period. Still another exampleis that the UE receives a DRX indicator directing to transition to thefirst DRX level from the BS. Still another example is that the UEreceives a setting value for a new Non-DRX level.

If the UE has a plurality of reception levels, power consumption of theUE can be adjusted depending on the amount of user data transmitted tothe UE. In an example of normally visiting a web page in Internetbrowsing, after downloading a web page, a user does not move to the nextpage while viewing the screen for quite some time. Data of the web pageare transmitted to the user all together. However, some of the data,e.g., a few pictures configuring the web page, are delayed when beingtransmitted to the user depending on situation. In this situation, theUE operates in the Non-DRX level when the screen is transmitted at atime, transitions to the second DRX level in which some of the data canbe delayed in the next stage, and finally, transitions to the first DRXlevel in which data transmission is almost needless while the user viewsthe web page. If the number of DRX levels of the UE is large, powerconsumption of the UE can be reduced by differentiating DRX levels inaccordance with the flow of the user data. Furthermore, degradation inquality of service felt by the user also can be minimized.

FIG. 5 is an example showing a method of receiving data according toanother embodiment of the present invention. A timer is used totransition between reception levels.

Referring to FIG. 5, a UE is initially in a first DRX level. If a BS hasa first data D1 to transmit, the BS informs the UE of the existence ofthe first data in line with a first DRX level period through ascheduling channel. The UE recognizes the scheduling channel, entersinto a Non-DRX level, and receives the first data D1.

After transmission of the first data D1 is completed, a transition timerstarts. If the UE does not receive its information through thescheduling channel until the transition timer expires, the UE cantransition to another reception level. Here, when the transition timerexpires, the UE transitions from the Non-DRX level to a second DRXlevel. The duration of the transition timer can be stored in a memory,can be informed to the UE by the BS or can be assigned by the UE andinformed to the BS.

FIG. 6 is an example showing a method of receiving data according tostill another embodiment of the present invention. A plurality of timersis used for transitioning between reception levels.

Referring to FIG. 6, a UE is initially in a first DRX level. If a BS hasa first data D1 to transmit, the BS informs the UE of the existence ofthe first data in line with a first DRX level period through ascheduling channel. The UE recognizes the scheduling channel, entersinto the Non-DRX level and receives the first data D1.

After transmission of the first data D1 is completed, a first transitiontimer starts. If the UE does not receive its information through thescheduling channel until the first transition timer expires, the UE cantransition to another reception level. Here, when the first transitiontimer expires, the UE transitions from the Non-DRX level to a second DRXlevel.

When the UE transitions to the second DRX level, a second transitiontimer starts. If the UE does not receive its information through thescheduling channel until the second transition timer expires, the UE cantransition to another reception level. Here, if the second transitiontimer expires, the UE transitions from the second DRX level to the firstDRX level.

FIG. 7 is an example showing a method of receiving data according tostill another embodiment of the present invention. A predeterminednumber of DRX level periods are processed for transitioning betweenreception levels.

Referring to FIG. 7, a UE is initially in a first DRX level. If a BS hasa first data D1 to transmit, the BS informs the UE of the existence ofthe first data in line with the first DRX level period through ascheduling channel. The UE recognizes the scheduling channel, entersinto a Non-DRX level and receives the first data D1.

After transmission of the first data D1 is completed, the UE transitionsto a second DRX level. The transition can be performed by a DRXindicator or a timer. If the UE does not receive its schedulinginformation for a predetermined number of second DRX level periods, theUE transitions to the first DRX level. Here, the UE transitions to thefirst DRX level after three second DRX level periods are elapsed.

The number of DRX level periods can be a value that is previously knownboth the BS and the UE or can be informed to the UE by the BS or viceversa.

FIG. 8 is an example showing a method of receiving data according tostill another embodiment of the present invention. This is a case wherea first DRX level is not synchronized with a second DRX level.

Referring to FIG. 8, if a UE does not receive its scheduling informationfor a predetermined number of second DRX level periods, it transitionsto a first DRX level. Here, the UE transitions to the first DRX levelafter three second DRX level periods are elapsed. At this point, the UEtransitions to the first DRX level immediately after the predeterminednumber of the second DRX level periods is elapsed.

FIG. 9 is an example showing a method of receiving data according tostill another embodiment of the present invention. This is a case wherea first DRX level is synchronized with a second DRX level.

Referring to FIG. 9, although a UE does not receive its schedulinginformation for a predetermined number of second DRX level periods, itcontinues to be in a second DRX level until a first DRX level issynchronized. It is assumed that the number of the second DRX levelperiods is set to three, and if the first DRX level is not synchronizedeven after three second DRX level periods are elapsed, the second DRXlevel is continued until a new first DRX level period is started. Atthis point, the set number of the second DRX level periods means aminimum number of repetitions.

FIG. 10 is an example showing a method of receiving data according tostill another embodiment of the present invention.

Referring to FIG. 10, a starting point of a DRX level period ispreviously determined. Accordingly, although a UE receives a DRXindicator after transmission of first data D1 is completed, it does notimmediately stop receiving a scheduling channel but the UE maintains theNon-DRX level until next second DRX level period is arrived. Thereafter,the UE transitions to a second DRX level in line with the start of asecond DRX level period. Although a BS transmits a DRX indicatordirecting transition to the second DRX level after transmitting thefirst data D1, the UE transitions form a Non-DRX level to the second DRXlevel at a time point when the next second DRX level period is started.

Next, while operating in the second DRX level, if the UE receives itsinformation in the first period of the second DRX level period throughthe scheduling channel, it transitions to the Non-DRX level again.

The network and the UE can previously know the starting point and/or theinterval of a DRX level period. Or the network can transmit informationon the starting point and/or the interval to the UE. If the startingpoint and/or the interval of a DRX level are set, when the UEtransitions from one reception level to another reception level, it canbe known that when the UE transitions to another reception level andfrom when the UE receives the first subframe of the new reception level.If a condition for transitioning the UE from a reception level to a newreception level is satisfied, the UE does not immediately transition tothe new reception level, but transitions in line with the starting pointof the newly set reception level. That is, the UE does not transition tothe new reception level at any time, but the new reception level beginsto be applied only to a predetermined time period based on the startingpoint and the interval of each reception level.

The UE having received second data D2 transitions form the Non-DRX levelto the first DRX level when a new first DRX level period starts. Whilestaying in a reception level, the UE can transition from the receptionlevel to a new DRX level if a new starting point of a DRX leveldifferent from the current reception level is arrived. For example,while the UE operates in the second DRX level and a certain condition issatisfied, if a new starting point of the first DRX level is arrived,the UE transitions to the first DRX level. Here, the certain conditioncan be that the UE does not receive its scheduling information for acertain period of time in the current reception level.

If the starting point of each DRX level is previously set, although theUE does not separately receive an indicator, such as a DRX indicator,and the settings of the UE and the BS do not match to each other, theaffect of the mismatch can be minimized. Although the UE misses the DRXindicator in a reception level, the UE wastes battery power as much asthe first DRX level period in maximum. Therefore, it is advantageous forthe UE and the BS to previously know the starting point of a DRX levelperiod. For this purpose, when a certain condition is satisfied and theUE transitions to a new DRX level, the UE does not immediatelytransition to the new DRX level, but only needs to transition in linewith the starting point of the new DRX level period.

For example, an operation described below is also possible.

-   -   1) A BS sets a first DRX level period and a second DRX level        period of a UE.    -   2) In a first subframe of the first DRX level period, the UE        examines a L1/L2 control channel to confirm whether data has        been arrived at the UE.    -   3) If data has been arrived at the UE, the UE        -   (1) receives the data based on scheduling information, and        -   (2) continuously monitors the L1/L2 control channel until a            DRX indicator is received, and if the BS informs existence            of data through the L1/L2 control channel, receives the data            based on scheduling information.        -   (3) If a DRX indicator is received, the UE            -   A) starts to operate in a second DRX level until the                next first DRX level period is arrived, and            -   B) receives the first subframe of each second DRX level                period while operating in the second DRX and examines                the L1/L2 control channel to confirm whether data has                been arrived at the UE.            -   C) If it is confirmed that data has been arrived at the                UE, the UE                -   i) receives the data based on scheduling                    information, and                -   ii) receives the L1/L2 control channel until there                    is no more data for the UE to receive.            -   D) If the UE confirms that it is not scheduled any more                through the L1/L2 control channel, the UE enters into a                sleep mode until the first subframe of either of the                second DRX level period or the first DRX level period,                which arrives first, is arrived.    -   4) If any data has not been arrived at the UE in the first        subframe of the first DRX level period, the UE operates in a        sleep mode until the first subframe of the next first DRX level        period is arrived.

While operating in a DRX level, if it is directed to receive data ornotified with existence of data to receive, through a scheduling channelor the like, a UE transitions to a Non-DRX level. Thereafter, if the UEreceives a DRX indicator, it transitions to a new reception level, e.g.,a new DRX level. The UE can update a currently used DRX setting valuewith a newly received DRX setting value.

A BS can additionally inform that when the new DRX setting value startsto be applied. When the UE receives the new DRX setting value, the newsetting value is used from a time point directed by the BS.

A Non-DRX level is, in other words, the same as a DRX level period ofzero. Accordingly, if a new DRX level period value of the UE is set tozero, the UE can operate in the Non-DRX level until a new DRX levelperiod value is set.

FIG. 11 is an example showing a method of receiving data according tostill another embodiment of the present invention.

Referring to FIG. 11, there is a plurality of operation modes in a UEdepending on the number and operation of reception levels. In ‘OPTION 1’mode, the UE has a DRX level and a Non-DRX level without a sleep mode.In ‘OPTION 2’ mode, the UE has a DRX level and a Non-DRX level with asleep mode. In ‘OPTION 3’ mode, the UE has two DRX levels and a Non-DRXlevel. Three operation modes are described here, but there may be morethan two or four operation modes.

In the ‘OPTION 1’ mode, the UE wakes Lip at the second period of thefirst DRX level period. At the first subframe of the second period ofthe first DRX level period, the UE confirms existence of its datathrough scheduling information and enters into the Non-DRX level. The UEreceives data during the entire second period of the first DRX levelperiod where it has waken up. If its data is not in the first subframeof the third period of the first DRX level period, the UE transitions tothe DRX level again.

In the ‘OPTION 2’ mode, the UE wakes up at the second period of thefirst DRX level period. At the first subframe of the second period ofthe first DRX level period, the UE confirms existence of its datathrough scheduling information and enters into the continuous receptionlevel. While continuously receiving data after waking up, if the UE isnot scheduled any more, it immediately transitions to the sleep mode. Ifits data is in the first subframe of the third period of the first DRXlevel period, the UE continuously receives data again. If its data isnot in the first subframe of the third period of the first DRX levelperiod, the UE transitions to the DRX level again.

In the ‘OPTION 3’ mode, the UE wakes up at the second period of thefirst DRX level period. At the first subframe of the second period ofthe first DRX level period, the UE confirms existence of its datathrough scheduling information and enters into the continuous receptionlevel. While continuously receiving data after waking up, if the UE isnot scheduled any more, it automatically transitions to the second DRXlevel. Next, the UE receives the first subframe of every second DRXlevel period until the next first DRX level period starts. If the UE isscheduled in the first subframe of the second DRX level period, it wakesup and continuously receives data during the entire second DRX levelperiod. If its data is not in the first subframe of the third period ofthe first DRX level period, the UE transitions to the first DRX levelagain.

Hereinafter, a DRX method related to uplink transmission is described.

Generally, when a UE transmits data or a control message to a BS, aresponse message is immediately transmitted from the BS. At this point,it is advantageous to use a DRX level having short DRX level period or aNon-DRX level.

If the UE transmits data or a control message to the BS, the UE changesa reception level that is being used. A new reception level can be theNon-DRX level or a new DRX level. When the UE transitions to a newreception level after performing uplink transmission, the new receptionlevel is previously determined when a call is established orreestablished. For example, after performing uplink transmission in thefirst DRX level, the UE can transition to the second DRX level.Alternatively, after performing uplink transmission in the first DRXlevel, the UE can transition to the Non-DRX level.

When the UE requests to allocate radio resources, it can transition tothe Non-DRX level. For example, if the UE uses an RACH, it transitionsto the Non-DRX level after transmitting a preamble. If radio resourcesfor transmitting data or a control message is allocated to the UEthrough the scheduling channel as a response to the RACH, the UE cantransition to a second DRX level.

FIG. 12 is an example showing a method of transmitting data according toan embodiment of the present invention.

Referring to FIG. 12, a UE is initially in a first DRX level. The UEtransmits data DU to a BS. After transmitting data D1 to the uplinkwhile operating in the first DRX level, the UE transitions to a secondDRX level. Alternatively, the UE can transition to a Non-DRX level, notto the second DRX level, depending on setting. The time point when theUE transmits data to the uplink can be the same as the tine point whenthe UE transitions to the second DRX level, or the former can precedethe latter, or the latter can precede the former.

After transitioning to the second DRX level, the UE searches for thefirst subframe of every second DRX levels and confirms whether its datais transmitted from the BS. After transitioning to the second DRX level,if the UE does not receive any data from the downlink for a certainperiod of time or does not receive any information, through thescheduling channel, the UE transitions to the first DRX level again. Ifthe UE endlessly operates in the second DRX level after transitioning tothe second DRX level after the uplink transmission, it can cause a badeffect on the power consumption of the UE. The certain period of time iscounted using a timer after the UE performs transmission, or the certainperiod of time may mean the number of the second DRX level periods inwhich the UE stays after performing transmission. The certain period oftime of the UE can be set through a call establishment or callreestablishment.

While operating in the second DRX level, the UE can transition to thefirst DRX level again at the starting point of the first DRX levelperiod. Alternatively, a DRX indicator can be used.

The steps of a method described in connection with the embodimentsdisclosed herein may be implemented by hardware, software or acombination thereof. The hardware may be implemented by an applicationspecific integrated circuit (ASIC) that is designed to perform the abovefunction, a digital signal processing (DSP), a programmable logic device(PLD), a field programmable gate array (FPGA), a processor, acontroller, a microprocessor, the other electronic unit, or acombination thereof. A module for performing the above function mayimplement the software. The software may be stored in a memory unit andexecuted by a processor. The memory unit or the processor may employ avariety of means that is well known to those skilled in the art.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims. Therefore, allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are intended to beembraced by the appended claims.

1. A method of transitioning a reception level to monitor a schedulingchannel in a wireless communication system, carried in a user equipment(UE), comprising: starting a first timer when a scheduling channelindicates a transmission or reception of data by a base station;monitoring continuously the scheduling channel in a non-discontinuousreception (Non-DRX) level while the first timer is running; when thefirst timer is expired, transitioning to a first DRX level with a firstDRX period and starting a second timer; monitoring discontinuously thescheduling channel in the first DRX level; and when the second timer isexpired, transitioning to a second DRX level with a second DRX period,wherein the first DRX period is shorter than the second DRX period. 2.The method of claim 1, further comprising: monitoring discontinuouslythe scheduling channel in the second DRX level; and when the schedulingchannel in the second DRX level indicates a transmission or reception ofdata by the base station, transitioning to the Non-DRX level andstarting the first timer.
 3. The method of claim 1, further comprising:when the scheduling channel in the first DRX level indicates atransmission or reception of data by the base station, transitioning tothe Non-DRX level and starting the first timer.
 4. The method of claim1, further comprising: receiving, from a base station, a message toconfigure a first discontinuous reception (DRX) level and a second DRXlevel.
 5. The method of claim 1, wherein the scheduling channel is apaging indicator channel.
 6. The method of claim 1, wherein thescheduling channel is a paging channel.
 7. A user equipment (UE)comprising a processor configured to: start a first timer when ascheduling channel indicates a transmission or reception of data by abase station monitor continuously the scheduling channel in anon-discontinuous reception (Non-DRX) level while the first timer isrunning; when the first timer is expired, transition to the first DRXlevel with a first DRX period and start a second timer; monitordiscontinuously the scheduling channel in the first DRX level; and whenthe second timer is expired, transition to a second DRX level with asecond DRX period, wherein the first DRX period is shorter than thesecond DRX period.
 8. The UE of claim 7, wherein the processor isconfigured to: monitor discontinuously the scheduling channel in thesecond DRX level; and when the scheduling channel in the second DRXlevel indicates a transmission or reception of data by the base station,transition to the Non-DRX level and start the first timer.
 9. The UE ofclaim 8, wherein the processor is configured to: when the schedulingchannel in the first DRX level indicates a transmission or reception ofdata by the base station, transitioning to the Non-DRX level andstarting the first timer.
 10. The UE of claim 7, wherein the processoris configured to receive, from a base station, a message to configure afirst discontinuous reception (DRX) level and a second DRX level. 11.The UE of claim 7, wherein the scheduling channel is a paging indicatorchannel.
 12. The UE of claim 7, wherein the scheduling channel is apaging channel.